Photographic material as referred to herein is understood to be generally planar, may comprise film or paper, may produce a black-and-white or color image, and may be in a continuous web form or may comprise discrete sheets.
Silver halide photographic materials are well-known, and are processed to generate a silver or dye image via a development stage followed by a series of baths to stabilize and provide permanence to the image. Such baths convert and remove unwanted materials from the coated photographic layers which would either interfere with the quality of the final image or cause degradation of the image with time. In typical color systems the development stage is followed by a bleach stage to oxidize the developed silver to a form which can be dissolved by a fixing agent in the same or a separate bath. Such silver removal stages are then followed by a washing stage using water, or other wash solution, or a stabilization stage using a stabilizer solution. For convenience, this last-mentioned stage will hereinafter be referred to generically as "washing." Such stages remove residual chemicals and may also include conversion reactions between stabilizer solution components and materials within the coated layers. These stages are required to provide the required degree of permanence to the final image.
In many cases, particularly in small-scale "minilab" or "microlab" equipment, the wash stage is performed in a multi-tank arrangement. Usually the replenishment of this stage, which keeps the concentration of substances removed from the photographic material at a constant and sufficiently low level, is carried out by adding fresh wash solution to the final tank of the sequence and arranging over-flow from the final tank to flow into the previous tank and so on, the overflow from the first tank of this stage being then discarded as effluent. This is referred to as a "counter-current" mode. This arrangement allows significantly lower amounts of solution to be used compared with one or two tanks especially when these are replenished separately.
In all of these arrangements, processing is carried out with the photographic material immersed in a tank of solution, even though many, though not all, photographic materials are sensitized with an emulsion only on one side thereof.
In a modern minilab a typical wash replenishment system might use around 200 cm.sup.3 of replenisher per m.sup.2 of sensitized material processed in a three or four-tank counter-current arrangement. The time the processed material spends in each tank is typically 20 to 25 seconds during which time an equilibrium is established between the concentration of substances in the coated material and the seasoned (steady-state) concentrations in the wash solution. The total time for this stage typically varies from 60 to over 100 seconds.
U.S. Pat. No. 5,365,300 discloses a process for the treatment of photographic material with a bath containing at least one processing material, in which, after the treatment bath, the photographic material is guided upwards through an ideally preferably vertical compartment which closely surrounds the material which is washed from above by water flowing under gravity in counter-current to the material. The wash water is arranged to carry chemicals off the material into the bath for re-cycling.
It is desirable to process photographic material more rapidly, and in particular to reduce overall wash times by several factors, for example to about 20 seconds as compared to 100 seconds, whilst reducing overall replenishment rates. Reduction of the path-length of the wash section of the process, for example, will shorten the time taken, for a given transportation speed of the material being processed. This latter parameter is usually constrained by the demands of the previous tanks. Unfortunately, simply reducing the number of counter-current tanks involved, while achieving the goal of shorter path-length, would require a significantly increased replenishment rate to achieve the same seasoned concentration (steady-state concentration) in the final tank from which the sensitized material emerges before being introduced to the drying stage.
It is also desirable to minimize the effluent from the processing. This is advantageous not only for the protection of the environment, but also to the operator, especially of mini- and micro-labs, in terms of having less solution for disposal.